The present invention relates to a swash plate type variable displacement compressor.
Japanese Laid-Open Patent Publications No. 5-172052 and No. 52-131204 disclose conventional swash plate type variable displacement type compressors (hereinafter, referred to as compressors). The compressors include a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores, which are formed in a housing. A drive shaft is rotationally supported in the housing. The swash plate chamber accommodates a swash plate, which is rotatable through rotation of the drive shaft. A link mechanism, which allows change of the inclination angle of the swash plate, is arranged between the drive shaft and the swash plate. The inclination angle is defined with respect to a line perpendicular to the rotation axis of the drive shaft. Each of the cylinder bores accommodates a piston in a reciprocal manner and thus forms a compression chamber. A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. An actuator is capable of changing the inclination angle of the swash plate and controlled by a control mechanism.
The actuator is arranged in the swash plate chamber, while being rotational integrally with the drive shaft. Specifically, the actuator has a rotation body rotating integrally with the drive shaft. The interior of the rotation body accommodates a movable body, which moves in the direction of the rotation axis of the drive shaft and is movable relative to the rotation body. A control pressure chamber, which moves the movable body using the pressure in the control pressure chamber, is formed between the rotation body and the movable body. A communication passage, which communicates with the control pressure chamber, is formed in the drive shaft. A pressure control valve is arranged between the communication passage and a discharge chamber. The pressure control valve changes the pressure in the control pressure chamber to allow the movable body to move in the direction of the rotation axis relative to the rotation body. The rear end of the movable body is held in contact with a hinge ball. The hinge ball is arranged in a center of the swash plate and couples the swash plate to the drive shaft to allow the swash plate to pivot. A pressing spring, which urges the hinge ball in such a direction as to increase the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
The link mechanism includes a hinge ball and an arm, which is arranged between the rotation body and the swash plate. The hinge ball is urged by a pressing spring arranged rearward to the hinge ball and maintained in contact with the rotation body. A first pin, which extends in a direction perpendicular to the rotation axis, is passed through the front end of the arm. A second pin, which also extends in a direction perpendicular to the rotation axis, is inserted through the rear end of the arm. The arm and the first and second pins support the swash plate with respect to the rotation body in a pivotal manner.
When a pressure regulation valve of the compressor is controlled to open, communication between a discharge chamber and a pressure regulation chamber is allowed. This raises the pressure in the control pressure chamber compared to the pressure in a swash plate chamber. The movable body thus retreats and presses the hinge ball rearward against the urging force of the pressing spring. This pivots the swash plate to decrease the inclination angle of the swash plate. The piston stroke is thus decreased. As a result, the compressor displacement per rotation cycle is reduced.
In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber. The movable body is thus moved forward and the hinge ball is operated correspondingly by the urging force of the pressing spring. This pivots the swash plate in the opposite direction to the corresponding direction of the case where the inclination angle of the swash plate decreases. The inclination angle of the swash plate is thus increased to increase the piston stroke.
However, the above-described conventional compressor operates the actuator such that the inclination angle of the swash plate is increased by lowering the pressure in the control pressure chamber. This makes it difficult to raise the compressor displacement rapidly.